分析:(1)先算小括號內的乘法,再算小括號內的加法,然后算中括號內的除法,再算中括號內的減法,最后算括號外的;
(2)分子分母同時計算,分子與分母中都先算括號內的,再算括號外的;
(3)先算小括號內的,再算小括號外的懲罰,然后算中括號內的減法,最后算括號外的除法;
(4)小括號內,把整數部分與分數部分分別相加,算出結果后,再算中括號內的除法,然后算中括號內的加法,最后算括號外的除法;
(5)先算括號內的,根據數字特點,括號內的算式寫成476.4×284+476.4×716,運用乘法分配律簡算,原式變?yōu)?780×99-4766×99,再次運用乘法分配律簡算.
解答:解:(1)[(1
×2+25)÷
-2
]÷1.6,
=[(
+25)÷
-2
]÷1.6,
=[
×
-2
]÷1.6,
=[
-
]÷
,
=
×
,
=
;
(2)
,
=
,
=
,
=
×
,
=
;
(3)[20-(1
+1
)×5
]÷120%,
=[20-
×
]÷
,
=[20-15]×
,
=5×
,
=
;
(4)[(11
+3
-12
)÷
+20.1]÷123.5,
=[(11+3-12+
+
-
)÷
+20.1]÷123.5,
=[(2+
)×
+20.1]÷123.5,
=[
×
+20.1]÷123.5,
=[4.6+20.1]÷123.5,
=24.7÷123.5,
=0.2;
(5)4780×99-(476.4×284+4764×71.6)÷1
,
=4780×99-(476.4×284+476.4×716)×
,
=4780×99-476.4×(284+716)×
,
=4780×99-476.4×1000×
,
=4780×99-4764×99,
=(4780-4764)×99,
=16×99,
=16×(100-1),
=1600-16,
=1584.
點評:此題考查了四則混合運算的順序,以及運用運算定律簡算的能力.